Winter forecast, part II: NOAA's predicts a warm winter for the Central U.S.

By: Dr. Jeff Masters , 2:51 PM GMT on November 21, 2008

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Let's follow up on yesterday's discussion about the long range forecast for the coming United States winter. Those of you outside the U.S. will probably be more interested in what the International Research Institute for Climate Prediction has to say for your country, and I encourage you to check out their excellent web site for their seasonal forecasts.

The official National Oceanic and Atmospheric Administration (NOAA) 90-day forecast for the upcoming winter, issued on November 20 by their Climate Prediction Center (CPC), calls for above average temperatures across the Central U.S. and Alaska. The remainder of the country has equal chances of above or below average temperatures. A dryer than average winter is expected over much of the Southern U.S., including the drought-stricken Southeast U.S.


Figure 1. Temperature forecast for the upcoming winter--December, January, and February 2009--made by NOAA's Climate Prediction Center. No areas of the country ar forecast to have an above-average chance of being colder than normal, but the Central U.S. has up to a 50% chance of having above-average temperatures.

How are the NOAA winter forecasts made?
NOAA uses several tools to make their forecasts. One key tool is their Climate Forecast System (CFS) model. This model includes a version of the GFS forecast model that we use for everyday weather and hurricane track forecasts. The CFS model also includes an ocean model that interacts with the atmospheric model. These models solve mathematical equations of fluid flow using a supercomputer for the entire globe, on a 100-km grid. NOAA also uses statistical models, which look at past winters and see how they depended on quantities such as sea surface temperature anomalies. Temperature trends are important, too--if it has been warmer than average the last ten years, it's a good idea to forecast a warmer than average winter.


Figure 2. Skill of the official 90-day forecasts issued 0.5 months in advance by NOAA's Climate Prediction Center. Note that the average skill over the past ten years is not very high (9 on a scale of 0 to 100), and has remained flat, indicating that our skill in making long-range forecasts has not improved.

How good are the NOAA winter forecasts?
NOAA rates its forecasts using the Heidke skill score, which is a measure of how well a forecast did relative to a randomly selected forecast. A score of 0 means that the forecast did no better than what would be expected by chance. A score of 100 depicts a "perfect" forecast, and a score of -50 depicts the "worst possible" forecast. For 90-day temperature forecasts issued 0.5 months in advance, NOAA has averaged a 9 out of 100 on the Heidke scale since 1995 (Figure 2). So, while there is some skill in forecasting what winter temperatures will be like, this skill is not much better than flipping a coin. Depressingly, Heidke skill scores for three-month precipitation forecasts are even worse, averaging just a one on a scale of 1 to 100 over the past 15 years.

Let's look at some examples. Last's year's winter temperature forecast issued in mid-November did poorly (Figure 3), failing to forecast that the U.S. would have equal areas with both above and below average temperatures. The 90-day forecast done in mid-November of 2005 for the winter of 2005-2006 was awesome, with a Heidke skill score of 45. However, the 90-day forecast done in mid-November of 2006 for the winter of 2006-2007 had virtually no skill, with a Heidke skill score of one.



Figure 3. Temperature forecast for Dec 2007-Feb 2008 issued by NOAA's Climate Prediction Center on November 15, 2007 (top). They predicted Equal Chances (EC) of either above or below-average temperatures for the Northwestern U.S. (white colored areas), and a 30-60% chance of above average temperatures over most of the remainder of the country. In reality, the U.S. experienced an average winter, with approximately equal areas of the country receiving above and below average temperatures (bottom). Image credit: National Climatic Data Center.

Why do seasonal forecasts do so poorly? Primarily, it's because the long-term weather patterns are chaotic and fundamentally unpredictable. To a lesser degree, we are limited by our imperfect physical understanding of what controls the climate, and our imperfect computer models we use to simulate the climate. As computer power continues to increase and our models include better representations of the weather and climate at finer grid sizes, I anticipate that seasonal forecasts will improve. However, given that long-range forecasts have not improved since 1995 despite a large increase in computer power, I doubt that this improvement will be more than 10-20% over the next thirty years.

Seasonal forecast models vs. climate models
A common complaint one hears about global warming predictions made by climate models is, "How can we trust the predictions of these climate modes, when they so such a lousy job with seasonal forecasts?" It's a good question, and there is no doubt that seasonal forecasts have pretty marginal skill. However, there is a fundamental difference between making a seasonal forecast and making a 100-year climate forecast. A seasonal or a short-term weather forecast is what mathematicians call an "initial value" problem. One starts with a set of initial meteorological and oceanographic values that specify the initial state of the planet's weather, then solve the equations of fluid flow to arrive at the state of the atmosphere a few days, weeks, or months into the future. This forecast is highly sensitive to any imperfections one has in the initial conditions. Since there are large regions of the atmosphere and ocean we don't sample, it's guaranteed that the prediction will suffer significantly from imperfect initial conditions. Furthermore, the chaotic and turbulent nature of the atmosphere leads to many "bumps" in the weather pattern over time scales of days, weeks, and months. The nature of turbulence makes it impossible to accurately forecast these "bumps" that are superimposed on the mean state of the climate.

A 100-year climate forecast, on the other hand, is what mathematicians call a "boundary value" problem. Given an initial and final set of factors (called "forcings") that influence the climate, one runs a climate model 100 years into the future. The final state of the climate will depend on the strength of the forcings supplied. This type of model is not very sensitive to initial conditions, and is not trying to forecast the "bumps" of chaotic, turbulent atmospheric motion superimposed on the mean climate. Rather, one is trying to forecast the mean climate. As computer power increases and our physical understanding of how the climate works grows, these type of models will continue to significantly improve. While climate models do fail to properly simulate important aspects of our past climate, such as the Arctic warming of the 1930s, and the observed 0.1°C global temperature increase that occurs at the peak of the 11-year solar sunspot cycle, they have been very successful at simulating things like the global cooling triggered by the 1992 Mt. Pinatubo eruption, and the observed pattern of greatest global warming in the Arctic. I believe that climate models are already significantly more reliable than seasonal forecast models, and should continue to improve steadily in coming years.

Support the Portlight Christmas for Gulf Coast Kids Honor Walk
Saturday is the portlight.org Christmas for Gulf Coast Kids Honor Walk. This is a fundraiser to buy gifts for the kids along the Gulf Coast who might not have much in their stockings this year because of the ravages of Hurricane Ike. Our own StormJunkie will be walking up the Arthur Ravenel Jr. Bridge in Charleston, SC, and will be taking his webcam along. Tune in to the webcam site at 2:30 pm EST to follow the walk, and participate in a live chat. Sponsorships of any amount, small or large, are appreciated! The cam will go active about an hour before the walk. It should be a cold but beautiful day.

Jeff Masters

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Leave it to MichaelSTL to threaten the "ignore" or "ban" when someone disagrees with AGW.

He banned me from his blog because of it. It's fine though. I have no room for those who are intolerant of critical thinking.
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735. IKE
8-14 day extended offers more global cooling....

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734. IKE
Global cooling offered in the 6-10 day extended.......

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New blog post up, and contest still on!
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Good evening all.
The NHC took 98L from green (?) , to yellow, to orange, in a couple hours. Whats up with that ? At that rate, it will be a Hurricane by midnight. Following the EXTRAP model, of course.LOL
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It's getting blasted by 30-40kt shear.

Though it could do a Barry, I guess.
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Trends say this is going to be a TS
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Appalachian Ski Mtn, North Carolina

Side-by-Side Ski Conditions
Last Updated: 11/23/08
Base Snow: 48 - 60"

-weatherunderground


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Quoting twistermania:
NHC gives 96L slight chance (20% or less) of development.


Now it's orange.
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Quoting antonio28:


96L Its getting a lot of shear, and shear is forecast to remaind highly unfavorable for development, even thought yor are correct the persistance of this disturbance is unlikely lets see what NHC has to say about it in the upcoming TWO.


Not really. Shear is a bit high right now, but based off the shear tendancy maps it is decreasing to about 15-20 knts. So, it looks like shear is marginally favorable as long as it does not move too far north.

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You can send some of that our way North Cakalaky! We could use some snow to go with the silly season.
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They actually raised it to orange.
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Winter Storm Watch for northern N.C mountains.2-4inches of snow

This is realy early for the season.Winston Salem,which is in the piedmont got .5 of snow last Friday.
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NHC gives 96L slight chance (20% or less) of development.
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TROPICAL WEATHER OUTLOOK
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
700 PM EST SUN NOV 23 2008

FOR THE NORTH ATLANTIC...CARIBBEAN SEA AND THE GULF OF MEXICO...

A BROAD LOW PRESSURE SYSTEM LOCATED JUST NORTH OF PANAMA IS
PRODUCING A LARGE AREA OF SHOWERS AND THUNDERSTORMS OVER THE
SOUTHWESTERN CARIBBEAN SEA AND ADJACENT LAND AREAS. SHOWER AND
THUNDERSTORM ACTIVITY HAS INCREASED AND BECOME BETTER ORGANIZED
TODAY...AND SOME ADDITIONAL DEVELOPMENT OF THIS SYSTEM IS POSSIBLE
OVER THE NEXT COUPLE OF DAYS AS IT DRIFTS SLOWLY WESTWARD.
REGARDLESS OF WHETHER OR NOT A TROPICAL CYCLONE FORMS...HEAVY
RAINFALL AND LOCALIZED FLOODING WILL BE POSSIBLE OVER PORTIONS OF
PANAMA...COSTA RICA...AND NICARAGUA DURING THE NEXT COUPLE OF DAYS.



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“Indeed, global temperature records taken from ice cores, tree rings, and lake deposits, have shown that the Earth was actually slightly cooler (by 0.03 degrees Celsius) during the 'Medieval Warm Period' than in the early- and mid-20th century.”

The medieval warm period was from 800 to 1300 AD. So since then the earth has warmed 0.03 degrees Celsius. If you start your data from the little ice age then we have warmed a lot more. Like was mentioned it is hard to use short intervals of time to create trends. And the trends will look differently based on when you start and stop. I surmise using records from 1880 to 2008 and even less is some instances like only from the 1970’s is inaccurate. Given geologic time one hundred years is nothing.


This is only one region but still interesting.

North Atlantic

"A radiocarbon-dated box core in the Sargasso Sea shows that the sea surface temperature was approximately 1 °C (1.8 °F) cooler than today approximately 400 years ago (the Little Ice Age) and 1700 years ago, and approximately 1 °C warmer than today 1000 years ago (the Medieval Warm Period).[6]
During the MWP wine grapes were grown in Europe as far north as southern Britain."
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~Think all that science is going to overload me at midnight...

Thanks though STL, for providing statements with scientific links and basis, so we can read for ourselves rather than making sweeping assumptions and news cuttings. :)
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718. JRRP
Link
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Quoting stormpetrol:
96L been hanging around that area for almost a week before any official notice was taken of it, I just don't like its persistence.


96L Its getting a lot of shear, and shear is forecast to remaind highly unfavorable for development, even thought yor are correct the persistance of this disturbance is unlikely lets see what NHC has to say about it in the upcoming TWO.
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96L been hanging around that area for almost a week before any official notice was taken of it, I just don't like its persistence.
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If it is global average why would they not include The poles? "GISS has it as the 5th warmest probably because they include the poles and Antarctica." "NOAA uses a different analysis." Lack of consistency and changes in algorthims they use to determine temperature causes disbelief.
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Here in MI, the average temp has risen 1 farenheight degree since 1900. I see no reason to worry about global warming.
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705. PcolaDan

Always been a student of Tesla, a real unsung hero. Unfortunately 90% of people have no clue who he was.

L8tr
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621. theshepherd
625. Skyepony

Thanks for your responses. Just came in off the lake - beautiful boating weather, but wore completely out. Ha Ha...nap time, will be back later tonight.
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Quoting itsnotgw:
when you think of Tesla, does HAARP come to mind?

I admit it, had to look up HAARP, but yea it does. Guy was way ahead of his time. And there are still people trying to work on his idea of distributing electricity without wires using his theories.

Wardenclyffe Tower

Some of Tesla's More Notable Inventions
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be back gotta go set up the X mas tree :)
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And another. Ok I will stop. We can all agree we need a healthy planet with clean air and water. Not to mention not giving our money to the Middle East.


Link
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Quoting MichaelSTL:
Come on, when are you going to fold? You can't win, I have debunked every piece of misinformation and lies that you have posted so far.


Another conspiracy site for yaLink
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Quoting all4hurricanes:

I noticed that first that was awesome


LOL ya I remember post 510 but yours shows it yellow now mines green cause I saved it on my comp also WPB was there too
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Quoting all4hurricanes:
96L! 96L! 96L! 96L!
OMJ 96L formed! Rene is on it's way
X X
___
U
I died


LOL and he's still GREEN! LOL

(well according to the image I saved from last night)
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Quoting Hurricane4Lex:
looky what ya'll missed if you weren't here last night!



and yes noone here is experencing color blindness

I noticed that first that was awesome
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MichaelSTL

I'm still waiting for a graph for 1998-2008.

Yes, I read your response to mine, but please a graph of 1998-2008.

TIA.
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when you think of Tesla, does HAARP come to mind?
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96L! 96L! 96L! 96L!
OMJ 96L formed! Rene is on it's way
X X
___
U
I died
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Quoting surfmom:
Telsa did some very fascinating work in regards to energy(although there is much in regards to weapons I find horrifying)


You saw that show too, huh! Fascinating. And yea, he was a little scary.
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RE 690


I like the color Green that they put on there but how does that fit into the scale? LOL
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I sold my car last year and have never felt freer! I use my feet or take the free bus offered through the university. No more car maintenance or gas spending. Having a car is a trap.
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looky what ya'll missed if you weren't here last night!



and yes noone here is experencing color blindness
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689. HadesGodWyvern (Mod)
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Jeff co-founded the Weather Underground in 1995 while working on his Ph.D. He flew with the NOAA Hurricane Hunters from 1986-1990.